The present invention is directed to an explosive powder charge operated setting tool including a housing with a bolt guide projecting from a leading end of the housing with the bolt guide axially displaceable relative to the housing. A magazine for fastening elements extends laterally from the bolt guide and can be displaced relative to the bolt guide against the force of a spring counter to the setting direction of the setting tool.
Hilti Aktiengesellschaft markets an explosive powder charge operated setting tool with a magazine for fastening elements characterized as model X A41 X AM 72. A bolt guide mounting a magazine projects from the housing of this known setting tool. The magazine can be moved relative to the bolt guide parallel to the setting direction. A spring in the form of an annular spring is located between the magazine and the bolt guide and the spring presses the magazine against a shoulder of the bolt guide facing in the setting direction and shaped basically in a circumferentially extending manner. The magazine located at the bolt guide enables storage and automatic feed of a number of consecutively arranged fastening elements, such as nails or studs, positioned in guide bushings connected to one another in a belt-like manner. A spring-loaded slide serves for feeding the attachment members within the magazine towards the bolt guide.
The housing must be moved though a so-called "contact pressure travel" relative to the bolt guide so that the setting tool can be operated. Accordingly, in a first phase of the contact pressure travel a leading end of the bolt guide is pressed against the surface of a receiving material. During the displacement of the bolt guide along with a piston guide located adjacent the bolt guide, a firing arrangement located in the trailing end region of the housing is cocked, the firing arrangement can be actuated by a switch or trigger. In a second phase of the contact pressure travel a displacement of the magazine relative to the bolt guide takes place in the setting direction, until the magazine also contacts the surface of the receiving material. This second phase loads a spring effective between the bolt guide and the magazine.
After a fastening element has been driven into the receiving material, the driving piston returns to its original position by means of stored waste gasses developed by the explosive powder charge. After the setting process, the waste gasses flow through an appropriate opening from a storage space into the inside of the piston guide upstream of the leading end face of the piston. The waste gasses return the driving piston back into its original position.
When the setting tool is lifted off the receiving material following firing, the housing is displaced relative to the piston guide and the bolt guide. The prestressed spring acting between the bolt guide and the magazine displaces the magazine relative to the bolt guide into its original position. After the magazine has returned to its original position, another fastening element can be pushed into the bolt guide from the magazine through an opening located in the side of the bolt guide.
Since the axial displacement of the magazine relative to the bolt guide is small, the feed of another fastening element takes place directly after the setting tool has been lifted off the receiving material and directly after the driving piston has been accelerated into its original position by the stored waste gasses.
If a magazine containing long fastening elements is used, damage can occur in the region formed by the magazine of the bolt guide and also in the region of the setting direction side of the piston rod of the driving piston. When longer fastening elements are being driven, the working stroke of the driving piston is correspondingly longer and the explosive powder charge used is stronger, so that the waste gasses build up a greater pressure in the storage unit. The greater pressure causes a strong acceleration of the driving piston into its original position, so that it can rebound several times in the firing region and move in the setting direction until it is finally located in its original position by the residual pressure of the storage unit. In the course of the rebound of the driving piston, it can impact with its piston rod against a fastening element which is pushed at this particular point in time from the magazine to the bolt guide and is not yet completely housed in the bolt guide.